"There's a big voice in that big body," Groban said, adding, "and I think it's really brave of him as an actor to be in a room with all singers and belt it out that way. So God bless him."

The 25-year-old song was updated with some hip-hop superstars. "Snoop Dogg singing was hilarious," Brandy said, "You're used to him rapping all the time, so to hear him sing, 'We Are the World,' in key, it's pretty cool."

Lil Wayne took on verses originally sung by Bob Dylan. "I don't know how to sing," he said. "I approached it the way I knew how." (Side note: Lil Wayne had these parting words: "I want to say I think it's amazing what's been done for Haiti, but I also find it amazing what hasn't been done for New Orleans.")

Wyclef Jean urged celebs not to visit Haiti unless they're ready to get to work. "We don't need no photo ops right now," he said.

"Anybody that goes on the ground, takes a picture and jumps back on the plane," he continued, "you're on the wrong island."

A Paul Haggis-directed video for the revamped song, officially titled "We Are the World: 25 for Haiti," will premiere Feb. 12 during NBC's coverage of the opening ceremony of the Winter Olympics.